With image processing devices for performing moving image frame frequency conversion processing or moving image compression processing, it is common to perform motion detection processing on a moving image, and to perform processing using the detected motion vector (see Patent Document 1). With this motion detection processing, as a method generally employed, the block matching, iterative gradient method, and so forth are available.
This iterative gradient method has a feature capable of detecting the motion of a sub-pixel with simple computation, but is poor in precision regarding detection in increments of pixels, so in an ordinary case, detection of a motion vector is frequently performed by integrating values in increments of blocks.
Accordingly, heretofore, gradient method computing has been performed by employing a pixel of interest serving as an object from which a motion vector is detected, or all the pixels within a computation block set on the periphery of a pixel of interest. Ideally, a likely motion vector can be detected in the case of the pixels within the computation block having generally the same action.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 9-172621